{"id":"CURL-CVE-2016-5420","summary":"Reusing connections with wrong client cert","details":"libcurl did not consider client certificates when reusing TLS connections.\n\nlibcurl supports reuse of established connections for subsequent requests. It\ndoes this by keeping a few previous connections \"alive\" in a connection pool\nso that a subsequent request that can use one of them instead of creating a\nnew connection.\n\nWhen using a client certificate for a connection that was then put into the\nconnection pool, that connection could then wrongly get reused in a subsequent\nrequest to that same server that either did not use a client certificate at\nall or that asked to use a different client certificate thus trying to tell\nthe user that it is a different entity.\n\nThis mistakenly using the wrong connection could of course lead to\napplications sending requests to the wrong realms of the server using\nauthentication that it was not supposed to have for those operations.","aliases":["CVE-2016-5420"],"modified":"2026-04-25T16:17:50.274714Z","published":"2016-08-03T08:00:00Z","database_specific":{"last_affected":"7.50.0","affects":"both","CWE":{"id":"CWE-305","desc":"Authentication Bypass by Primary Weakness"},"URL":"https://curl.se/docs/CVE-2016-5420.json","package":"curl","www":"https://curl.se/docs/CVE-2016-5420.html","severity":"Medium"},"affected":[{"ranges":[{"type":"SEMVER","events":[{"introduced":"7.7"},{"fixed":"7.50.1"}]}],"versions":["7.50.0","7.49.1","7.49.0","7.48.0","7.47.1","7.47.0","7.46.0","7.45.0","7.44.0","7.43.0","7.42.1","7.42.0","7.41.0","7.40.0","7.39.0","7.38.0","7.37.1","7.37.0","7.36.0","7.35.0","7.34.0","7.33.0","7.32.0","7.31.0","7.30.0","7.29.0","7.28.1","7.28.0","7.27.0","7.26.0","7.25.0","7.24.0","7.23.1","7.23.0","7.22.0","7.21.7","7.21.6","7.21.5","7.21.4","7.21.3","7.21.2","7.21.1","7.21.0","7.20.1","7.20.0","7.19.7","7.19.6","7.19.5","7.19.4","7.19.3","7.19.2","7.19.1","7.19.0","7.18.2","7.18.1","7.18.0","7.17.1","7.17.0","7.16.4","7.16.3","7.16.2","7.16.1","7.16.0","7.15.5","7.15.4","7.15.3","7.15.2","7.15.1","7.15.0","7.14.1","7.14.0","7.13.2","7.13.1","7.13.0","7.12.3","7.12.2","7.12.1","7.12.0","7.11.2","7.11.1","7.11.0","7.10.8","7.10.7","7.10.6","7.10.5","7.10.4","7.10.3","7.10.2","7.10.1","7.10","7.9.8","7.9.7","7.9.6","7.9.5","7.9.4","7.9.3","7.9.2","7.9.1","7.9","7.8.1","7.8","7.7.3","7.7.2","7.7.1","7.7"],"database_specific":{"source":"https://curl.se/docs/CURL-CVE-2016-5420.json"}}],"schema_version":"1.7.5","credits":[{"name":"the curl security team","type":"FINDER"},{"name":"Daniel Stenberg","type":"REMEDIATION_DEVELOPER"}]}